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Apophyllite
Phyllosilicate mineral
Phyllosilicate mineral
| Field | Value | |
|---|---|---|
| name | Apophyllite | |
| category | Phyllosilicate minerals | |
| group | Apophyllite group | |
| boxbgcolor | #cccccc | |
| image | Apophyllite-65547.jpg | |
| imagesize | 260px | |
| formula | (K,Na)Ca4Si8O20(F,OH)·8H2O | |
| IMAsymbol | Apo | |
| color | Usually white, colorless; also blue, green, brown, yellow, pink, violet | |
| habit | Prismatic, tabular, massive | |
| system | Tetragonal | |
| symmetry | *P4/mnc* | |
| cleavage | Perfect on (001) | |
| fracture | Uneven | |
| mohs | 4.5–5 | |
| luster | Vitreous; pearly | |
| refractive | 1.536 | |
| birefringence | 0.000–0.003 | |
| pleochroism | Dichroic (colorless) | |
| streak | White | |
| gravity | 2.3–2.4 | |
| diaphaneity | Transparent to translucent | |
| other | [[Image:Radioactive.svg | 25px]] Radioactive 4.37% (K) |
| references |
The name apophyllite refers to a specific group of phyllosilicates, a class of minerals. Originally, the group name referred to a specific mineral, but was redefined in 1978 to stand for a class of minerals of similar chemical makeup that comprise a solid solution series, and includes the members fluorapophyllite-(K), fluorapophyllite-(Na), hydroxyapophyllite-(K). The name apophyllite is derived from the Greek grc (), meaning 'it flakes off', a reference to this class's tendency to flake apart when heated, due to water loss. Exfoliation of apophyllite is also possible by treating it with acids or simply by rubbing it. These minerals are typically found as secondary minerals in vesicles in basalt or other volcanic rocks. A recent change (2008) in the nomenclature system used for this group was approved by the International Mineralogical Association, removing the prefixes from the species names and using suffixes to designate the species. A subsequent nomenclature change approved by the International Mineralogical Association in 2013 renamed the minerals to include both suffixes and prefixes, as shown above.
Though relatively unfamiliar to the general public, apophyllites are fairly prevalent around the world, with specimens coming from some of the world's most well-known mineral localities. These localities include: Jalgaon, India; the Harz Mountains of Germany, Mont Saint-Hilaire in Canada, and Kongsberg, Norway, with other locations in Scotland, Ireland, Brazil, Japan, and throughout the United States.
Structure
Apophyllite has an unusual structure for a phyllosilicate. Whereas most phyllosilicates have a T layer (silica backbone) consisting of interlocked 6-fold rings of silica tetrahedra, with pseudohexagonal symmetry, the T layer in apophyllite consists of interlocked 4-fold and 8-fold rings of silica tetrahedra with true tetragonal symmetry. File:Apophyllite T.png|T layer (silica backbone layer) of apophyllite File:Apophyllite 100.png|Structure of apophyllite viewed in the {100} direction, parallel to layering File:Apophyllite unit cell.png|Unit cell of apophyllite
Species
- Fluorapophyllite-(K) (formerly fluorapophyllite, apophyllite-(KF)), KCa4Si8O20(F,OH)·8H2O – white, colorless, yellow, green, violet
- Hydroxyapophyllite-(K) (formerly hydroxyapophyllite, apophyllite-(KOH)), KCa4Si8O20(OH,F)·8H2O – white, colorless
- Fluorapophyllite-(Na) (formerly natroapophyllite, apophyllite-(NaF)), NaCa4Si8O20F·8H2O – brown, yellow, colorless
- Fluorapophyllit-(Cs) (new) CsCa4(Si8O20)F·8H2O
- Fluorapophyllit-(NH4) (new) NH4Ca4(Si8O20)F⋅8H2O
(India) Fluorapophyllite-(K) and stilbite.jpg|Fluorapophyllite-(K) and stilbite Apophyllite-(KF)-66684.jpg|Isolated Fluorapophyllite-(K) cluster on contrasting matrix Hydroxyapophyllite on white background.jpg|Hydroxyapophyllite Natroapophyllite-ind11b.jpg|Fluorapophyllite-(Na)
References
- MinDat Listing
- Mineral Galleries
- This describes the older definition as a specific mineral.
References
- Warr, L.N.. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine.
- "Radioactive Gems: ClassicGems.net".
- [http://webmineral.com/data/Apophyllite.shtml Apophyllite data on Webmineral]
- Burke, E.A.J. (2008): Tidying up mineral names: an IMA-CNMNC scheme for suffixes, hyphens and diacritical marks. Mineral. Rec., 39, 131–135.[http://rruff.info/uploads/MR39_131.pdf]
- (2013). "CNMNC guidelines for the use of suffixes and prefixes in mineral nomenclature, and for the preservation of historical names". European Journal of Mineralogy.
- (1993). "Manual of mineralogy: (after James D. Dana)". Wiley.
- (1 January 1993). "A neutron powder diffraction study of partially dehydrated fluorapophyllite, KCa4Si8O20F•6.9H2O". European Journal of Mineralogy.
- [http://www.mindat.org/min-1573.html Apophyllite-(KF) on Mindat]
- [http://www.mindat.org/min-1989.html Apophyllite-(KOH) on Mindat]
- [http://www.mindat.org/min-2851.html Apophyllite-(NaF) on Mindat]
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